There is evidence that various anatomical structures have altered morphology with ageing, and anecdotal evidence of changing lumbar spinous process (LSP) morphology with age. This study aims to clarify the influence of age on LSP morphology, and on lumbar spine alignment.

200 CT scans of the abdomen were reformatted with bone windows allowing precise measurement of LSP dimensions and lumbar lordosis. Observers were blinded to patient demographics. Inter-observer reliability was confirmed.

The smallest LSP is at L5. The male LSP is on average 2-3mm higher and 1mm wider than the female LSP. LSP height increases significantly with age at every level in the lumbar spine (P<10^-5 at L2). The LSPs increase in height by 2-5mm between 20-85 years of age (P<10^-6), which was as much as 31% at L5 (P<10^-8). Width increases proportionally more, by 3-4mm or greater than 50% at each lumbar level (P<10^-11). Lumbar lordosis decreases in relation to increasing LSP height (P<10^-4) but is independent of increasing LSP width (P=0.2).

The height and width of the spinous processes increases with age. Increases in spinous process height are related to a loss of lumbar lordosis and may contribute to sagittal plane imbalance.